The subject of this thesis has been defined with the aim of proposing new liquid-liquid extraction (LLE) processes applicable to the recycling of lanthanides and actinides at downstream of the nuclear fuel cycle. The proposed methodology relies essentially on the availability of lipophilic ligands derived from highly polar chelating agents such as poly(aminocarboxylic) acids (PACA) or hydroxamic acids (HA). As a first step, the PhD student will be involved in a major organic synthesis project, building up a library of several of these different derivatives. During the first phase of the thesis, the candidate will be allowed to develop his activity based on knowledge and results already acquired in this field at LTSM. In subsequent phases, he or she will be asked to develop new, more efficient and, in some cases, stereoselective (enantio- and/or diastereoselective) synthesis strategies when several stereoisomers can be obtained. Concomitantly to this, the candidate will be asked to characterize the extraction properties (affinity and selectivity) of the yielded ligands towards valuable lanthanides and actinides. This will be carried out using well proven approaches, enabling quantitative and qualitative monitoring of ELL performed on a scale of a few milliliters. The PhD student will be supervised throughout his thesis by two co-directors and a supervisor, who will provide him with multidisciplinary expertise.